In the past, as a method of manufacturing an open pore-type porous body for use in a catalyst carrier, a gas filter, a filter body, or the like, a method of manufacturing an open pore-type porous body having: a fine pore film on a surface of an open pore-type porous laminated body inclined such that fine pore diameters become successively smaller toward the surface; or a fine pore layer at a slight depth from the surface has been disclosed (for example, see Patent Document 1). This method is characterized in that a thin film or a surface layer is formed on a surface of the open pore-type porous laminated body through any one of a gas phase chemical reaction method, a vacuum deposition method, an ion plating method, and a sputtering method. According to this method, since it is possible to form the fine pore layer in from particle units to atom units, the arrangement of particles can be easily optimized, and thus the transmission performance and the separation performance of the layer can be improved.
A porous silica film formed by: coating a support with a silica sol obtained by hydrolyzing a reaction material including a silicon alkoxide, water, and nitric acid; and baking the support has been disclosed (for example, see Patent Document 2). In this porous silica film, many pores are formed in the silica film, a mean diameter of the pores is 1 nm or greater, and preferably 1 nm to 5 nm, and separation or filtering of nanoparticles from, for example, a liquid material such as water or an organic solvent is possible.